WT8821 High Precision Portable Digital Handheld Oxygen Alarm Detector Tester Meter Features: 1. This oxygen detector is widely used in industry and can be found in locations to monitor manufacture processes and emerging technologies. 2. With a large screen display the measured results, you can get oxygen concentration at a glance. 3. The gas detector can alert the operator in the area where the leakage occurred, giving them a chance to leave. 4. Widely used in chemical industry, electronic industry, underground operations, in-car oxygen detection. 5. Maximum/minimum hold feature for measuring absolute high/low peaks and hold data. 6. The product is ergonomically designed for easy handling and operation, perfect for household and working testing. Specification:  Item Type: Oxygen Detector  Material: ABS Measurement Range: 0-25% volume Maximum Overload: 30% oxygen Response Time: <15s Sensor Type: Electromagnetic oxygen sensor Ambient Humidity: 15-90%RH Power Supply: 3x1.5V AAA Battery (Not Included)  Package List:  1 x Oxygen Detector 1 x Instruction  1 x Black Box